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Written by Greg Gimlick
Electrics
Column
As seen in the April 2019 issue of
Model Aviation.


Electrics

the authors chosen method for lipo battery storage involves ammunition cans and a steel truck box
The author’s chosen method for LiPo battery storage involves ammunition cans and a steel truck box.

Learn More About Lipo Battery Basics

Visit www.ModelAviation.com/lipo-battery-basics.

I’m getting away from some of the technical stuff that I discussed in the last two columns, but the feedback to the internal resistance (IR) discussion has been interesting. Further discussion can be found online in the RCGroups "The BattIR Meter Version II" build thread.

Battery Storage

Flying season is upon us and we’re waking up and using our LiPo battery packs, so I want to discuss how to store them safely. Because we’re charging and often storing them that way, they’re more volatile than when they are put away at storage level.

I want you to think about your storage routine. We all have different circumstances, but it’s important to think hard about safety and your home.

I’m not an explosives ordnance expert, nor am I a physicist who can definitively say what is required to contain the forces that are released when a LiPo battery decides to ignite. I do know that much energy is released in a short period, and a lot of smoke and flames are involved. Most of the time the fire is short-lived, but the amount of smoke is enormous. If you saw magnesium burn in your high school chemistry class, that’s what it’s like.

I recently took a long, hard look at how I’ve been storing my battery packs and decided it wasn’t good enough. A concrete bunker would be the best option, but most of us don’t have the space for one. I determined my goals, and here’s how it broke down for me.

everything is stored in the locked box on top of a rolling stand
Everything is stored in the locked box on top of a rolling stand.

  • My number one concern is to contain a fire.
  • I want something to alarm me to a problem in the garage where batteries are stored.
  • I want to have an exit strategy for the stored batteries.
  • There should be signs to alert first responders to the presence of LiPo batteries.
  • It must also be convenient and help organize my battery packs.

Having laid out my goals, it was off to the internet, friends, and colleagues to sort out the methods employed by others. There was no sense in reinventing the wheel. I opted for the setup that I’m showing here. It might not be exactly right for your needs, but it could be a starting point. The parts count was small.

the can on the left has part of the seal still in place to provide the needed pressure for the latch to hold
The can on the left has part of the seal still in place to provide the needed pressure for the latch to hold. The can on the right has the dimples drilled out on top for vents. Either works well.

  • A steel truck box with locking handle.
  • A concrete backer board.
  • Ammunition cans.
  • LiPo bags.
  • Hazardous materials stickers for the outside door.
  • A smoke/fire alarm.
  • A wheeled base.

I picked up a steel truck box at my local Tractor Supply Co. store that had a small dent in the top. They discounted it enough to make it reasonable. The box has a rubber seal around the door, but it isn’t so tight that the box is airtight. It’s also big enough to store four ammunition cans side by side, with room on top of them.

Ammunition Can Considerations

I shopped around and found new ammunition cans online at Walmart for $10 each. They come airtight with a solid rubber seal around the top, but because I wanted to vent the can to prevent any explosion, I opted to try two methods.

On the first can, I drilled the dimples on the top to provide a series of 1/8-inch holes to vent smoke and pressure. The problem is that if I did decide to try to move the box while it is venting, the heat/fire would come through the holes around the handle.

On the rest of the boxes, I cut most of the seal out, leaving only enough to supply the pressure to help the lock stay shut. If you remove the entire seal, the top won’t be secure and will open when you pick it up by the handle. I prefer the partial seal because it vents the can downward and away from the handle. This is a personal choice, but don’t use a fully sealed can.

I usually put my packs into a LiPo bag then into the ammunition cans. It’s just another level of containment but probably overkill (if that’s possible) when talking fire safety.

A couple of companies sell wood divider kits so that you can stand the packs on end inside of the cans. If you do this, be sure to watch for wires that could get caught in the top of the can when you close it. That could easily cut the wires and short the pack. I also label each ammunition can with what size battery packs are inside.

Final Setup

My truck box sits on top of a concrete backer board on top of a rolling stand. The idea is that I might be able to roll the whole thing out onto the driveway should something go terribly wrong. It’s also very heavy, so the rolling stand makes it easy to move inside my shop.

The ammunition cans are loaded with batteries and stored in the truck box, and it all sits under an alarm in the shop. I do understand that if one of the packs goes, they all might, but I hope that each box will contain it well enough within the big box to minimize damage.

placing battery packs in a lipo bag before they go into an ammunition can serve as an extra measure of safety
01: Placing battery packs in a LiPo bag before they go into an ammunition can serve as an extra measure of safety. 02: If you store your packs upright, watch for wires that could catch in the top when closing the lid.

Wrapping Up

People fight over the best or only way to store LiPo batteries. Do your homework and think about how to increase the safety of your family and home while still enjoying the hobby. Send me photos and descriptions of your method of storage.

Sources:

The BattIR Meter Version II

https://bit.ly/2rJPKQH

18 comments

Great advice. You mention a STEEL truck box, but yours and the welds on it look very aluminum, except the lock. As we know aluminum burns! And LiPo cells are the perfect thing to get aluminum hot enough to burn. And even if not burning, aluminum loses its solid state into a liquid in a very abrupt fashion, no glowing red like steel. What is it, steel or aluminum. Try a magnet.

You are correct, good eye! This box is aluminum and not as good as a steel one would be. I ordered the steel version of it, but not in time for the photos I needed for the article.

Good article but I have a question on temperature ranges for battery storage. I have all of my batteries in a large bat safe and three .50 Cal ammo cans. My plan is to store and now charge them in a deck box outside for added safety. I don’t think I will have issues in the summer but will very cold weather ruin the batteries while stored?

I wish I could give you a dead perfect answer for storage temps. All manufacturers seem to agree the "optimum" temp would be 59 degrees, but they also give a range for "safe" storage and it's anything from 20 degrees F to 140 degrees F. I've seen some sources that say as high as 170 is okay for short periods of time, but I don't buy that. My storage area ranges from 45 degrees to 95 degrees. All say not to allow them to freeze, but nobody has told me what the freezing temperature of a lipo chemistry cell is.

Looks like a chain reaction bomb to me. Get some Batt-Safes. Sleep better knowing you have a proper solution.

Batt-Safes are a great solution and a great product. Unfortunately they don't offer one big enough to store over 100 batteries ranging from 3S 1200mAh to 6S 6000mAh. If they did, I'm sure it would be pretty expensive so I've done what I could to increase the safety of how I store them.

No avoiding the possibility of a chain reaction sort of keeping each pack separate in its own container.

I have 8 different lipo packs for 4 years now.i have never done the so called storage charge or any other gimmick type thing.when flying season is over they just go into my ammo box that I use all year.come flying time charge up and I am flying the season with no problems what so ever!!! Call it luck or whatever but 8 packs without missing a heartbeat seems normal.never seen a pack blow up.some guys at the club there packs are puuffed.... while all mine are normal....I geussy must be that luck of charm I have!!

Storing at "storage level" is no gimmick. The definition of what that is might be interpreted a dozen ways depending who you ask. For me...and the battery design engineer I consulted, it's anything between fully charged and fully discharged. Leaving it fully charged or fully discharged will quickly convince you storing them at some other level is justified. I leave them around 3.8V per cell, but if it's anywhere in there, I'm good with it. I have packs that are several years old and performing fine. My oldest acceptable pack is now 10 years old. It has declined but is fully usable and the IR values of the cells are nicely matched. I am more particular than most when it comes to not leaving them fully charged or discharged, but my results satisfy me. Lipos are expensive and deserve some attention.

To make your case really safe it should be lined with a fireproof material. Drywall, yep that stuff all over your home. Line the box so the sides hold up the top. Use some high temp glue to assist. Easy and done. You can find much more about this on line.

This is a great suggestion and one I have implemented. This is the product I used:
https://www.homedepot.com/p/Sheetrock-Firecode-Core-5-8-in-x-4-ft-x-8-ft...

A ticking chain reaction time bomb. Get Batt-Safes, do it right. This is a very dangerous article.

Comments like this are not helpful to anyone and simply try to bait arguments. I suggest you write a proper article on the subject and submit it to the editors for publication. Quality content is always in demand and they'd be glad to receive some.

Batt-Safes are great devices, no argument from me.

Instead of a box, you might consider using a discarded built-in oven. A self cleaning electric oven is insulated for a 700 to 900F temperature during a cleaning cycle and are very compact. You can get discarded ones at appliance stores that install new ones for a junk price. Electrics are best. This will help contain the heat of a fire for some time. I use a self standing electric oven for my storage. And charge my batteries atop its cooking surface. Most electrics have enamel surfaces and will not conduct electricity.

Good idea Gary, this is one I hadn't heard before and makes good sense. Thanks for suggesting it to people

Do you store batteries charged

I do not store my batteries charged, at least not fully charged. I store them around 3.8V per cell, but anywhere in that area is fine. The key is not to leave them fully charged or fully discharged. If I come back from flying and a pack is 3.9V per cell, that's okay with me and I store it that way. If I have packs still fully charged, I do a partial discharge to get them around storage level if I'm not going out the next day.

I like the cart idea but do not like chain reaction possibility at all. I have a metal cart looking for a use and this is great new use. It is two teired (2 shelves) so will hold 6 - 8 ammo cans easily. It was bought at Sam's club for$59. Great New use! !!!!!!
Thanks for great idea!!!!!
Dave

As stated in the beginning of my article, the purpose was to get you thinking about how you're storing your lipos and how you might do it better. I'm not an engineer and won't engage in public flame wars over the subject. You folks are offering some great suggestions and they are appreciated. Any constructive criticism is always welcome.

Those of us who have been writing about electrics are concerned with people doing things safely and we risk some harsh remarks when we attempt to educate and get people thinking about safety. That's part of it, but you'd be shocked at how many people send me photos and emails that show they leave charged lipo packs in planes, on benches and some even in cars between flying sessions.

My mode of storage works for me and offers something to get you thinking of what will work for you. My first experience with lipos was with Gen 1 cells when we got them in individual envelopes ready to be assembled into whatever size packs we wanted. We didn't even use balance plugs in those days. In all these years, I've had one pack go up in smoke and that was because I crashed an EDF and the pack ruptured on impact.

I store all of my 100+ packs in this setup I showed. It would be great to have about 50 Batt-Safes to use, but that's out of the question.

Be safe and think about your storage routine, that's all I ask.

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